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5 Best Weed Killers For St. Augustine Grass

Best Weed Killers For St. Augustine Grass

Most recommended
Southern AgSouthern Ag Surfactant for Herbicides Non-Ionic
  • 16 oz.
  • Non-ionic surfactant
  • Increases herbicides effect

A good choice too
The AndersonsThe Andersons Pro Turf Barricade Granular Pre-Emergent Weed Control
  • 50lb
  • 0,48% Barricade
  • Easy to Use

A good choice too
Hi-YieldHi-Yield Atrazine Weed Killer
  • Size: 32 oz
  • Active ingredient: 4% atrazine
  • Easy to use

Southern AgSouthern Ag Atrazine St. Augustine Grass Weed Killer
  • 1 Gallon
  • Kills broadleaf weeds
  • 4% Atrazine

PBI GordonPBI GORDON SpeedZone Lawn Weed Killer Boadleaf Herbicide
  • 1 Gallon
  • Fast weed control
  • Visible activity in hours

Choose the Best Weed Killer For St. Augustine Grass

Customer’s Choice: the Best Rated Weed Killers For St. Augustine Grass

563 users answered this survey. Please help us improve this review!

57.73% of users selected Southern Ag Surfactant, 9.59% selected The Andersons, 13.32% selected Hi-Yield, 12.26% selected Southern Ag and 7.1% selected PBI Gordon. Every month we analyze your answers and change our rating.

Florida, the Carolinas, and Southern California are the U.S. states where you can find St. Augustine weed growing on your lawn. This turfgrass makes a thick green lawn in warm coastal areas. But without proper maintenance (fertilization is a must-do thing) this grass/weed can quickly become a problem for any homeowner.

There are some remedies capable of fertilizing and at the same time controlling the growth of St. Augustine. Check the best multi-purpose weed killers that you may use for controlling St. Augustine.

Southern Ag Surfactant for Herbicides – the best for killing St. Augustine weeds with herbicides!

Amine Weed KillerThis surfactant stands for 80% non-ionic wetting agent. It improves the action of any herbicide providing its better penetration and coverage. Southern Ag Surfactant is compatible practically with any herbicide brand that comes to mind – Trimec, Atrazine, Brush Killer, to name the few.

Tips for users: 1 teaspoonful of this product is usually enough to boost 1 gallon of any herbicide (you may need a higher dosage for boosting Round-up and MSMA) – but check the label directions before mixing two products.

  • It will work not only with broadleaf and turfgrass weeds but also with poison ivy, sumac, Bermuda, horsetail
  • More effective than liquid (dish) soap for improving herbicides
  • Compatible with most herbicides and fertilizers (try mixing it with blue dye)
  • Compatible with hose-end sprayers
  • Efficient use
  • Quick action
  • Be careful! It may kill flowers and herbs if used improperly
  • Check the label instructions – if you take too much of this product, it will just act as a fertilizer
  • Won’t kill all weed types
  • Some users think that its price is high

This product is good only for mixing with herbicides to kill weeds. Never apply just this remedy – it won’t work. It is recommended only for improving the effectiveness of your regular herbicide.

The Andersons Pro Weed Killer – the best pre-emergent product for St. Augustine weeds!

The Andersons Pro Turf Barricade Granular Pre-Emergent Weed ControlA powerful turf granular weed killer of the pre-emergent method of action. It acts as an efficient spot weed killer. It is fully compatible with the edge spreader (the settings are 4 – 7.5).

The Anderson Pro product can be spread all over the garden area including rock gardens and the areas under the trees. It is enough to treat the lawn with it twice per year – in the spring and fall.

  • One of the best pre-emergent treatments for killing broadleaf weeds
  • Easy instructions to follow
  • May act as a great spot weed killer
  • May not work in some regions – uses claim that it may work in Georgia, but won’t affect in West Texas
  • Pricey
  • Won’t work in late winter or late autumn

This product may not work if applied in too cold or too hot weather – the best temperature for applying is around 500F. Use this treatment only twice per year and you won’t have any summer weeds.

Hi-Yield Atrazine Weed Killer – the best for killing almost any weeds anytime!

Hi-Yield Atrazine Weed KillerVoluntary Purchasing Group manufactured the product – Hi-Yield Atrazine weed killer – for destroying St. Augustine and similar weeds. It is based on a very effective component – 4% atrazine.

One of the best properties of this product is high concentration – use ½ cup (1 oz) per gallon.

  • The concentrated product
  • Easy to apply
  • The coverage area is 3720 square inches
  • Compatible with hose-end sprayers
  • Won’t harm vegetables and fruits
  • Good for spot weed control as well
  • Apply carefully, according to the directions – otherwise, you will destroy all grass in your backyard
  • The shelf life is not long – about a few months
  • You must invest in nutrients and fertilizers after applying this product

It will take from 2 to 4 weeks to see the result after the application. At first, the weeds turn yellow and only then dry. Test it on a small area before covering the whole lawn – it may not work in some regions or may kill good grass as well.

Southern Ag Atrazine – the best post-emergent weed killer for broadleaf and grassy weeds!

Southern Ag Atrazine St. Augustine Grass Weed KillerSouthern AG weed killer is another powerful 4% atrazine remedy for controlling St. Augustine and centipede grass. For covering about 500 square feet it is enough to use 4.33 ounces per 1 gallon of spray (take 2 gallons of water and about 9 ounces of the product to cover 1,000 sq. ft.).

Tips for users: Do not use this product as a pre-emergent weed treatment – only for post-emergent action, though Atrazine in other remedies is usually good for both effects. Do not apply while the grass is dormant. Never spread on sweet corn. It is good for applying when the temperature range is around 500F – mostly, in early spring. Do not irrigate for 72 hours after the application.

  • It is efficient and cost-effective
  • Good for controlling emerged weeds and weeds from seeds
  • Large coverage area – 60,000 sq. ft.
  • Besides lawn, you may use it for killing weeds on ditch banks, golf courses, parks and along fences
  • Not compatible with hose-end sprayers – instead use a pump sprayer
  • Won’t kill Spurweed or Poa Annua weed
  • Do not let your pets swallow this product – it is extremely toxic
  • May cause harm to turf, flowers, veggies, and fruits

It is better to use this product in early spring. The first results will be evident in 2 weeks. Sometimes you may need to apply the double dosage to achieve the best effect. In addition, it won’t be helpful if the product is applied with a surfactant.

PBI/Gordon Speed Zone Weed Killer – the best for large property owners!

PBI GORDON SpeedZone Lawn Weed Killer Boadleaf HerbicideThis weed killer delivers fast results on large properties like backyards, parks, farms. It is a pre-emergent product that effectively kills even emerged weed types. One of the best remedies for the fast killing of St. Augustine weed – the results become visible in a few days, if not hours.

  • Highly concentrated
  • Won’t harm any turfgrass or lawn grasses
  • Visible results may appear in a few hours
  • Cost-effective
  • One gallon may destroy the weeds on the large area – up to 18,000 sq. ft.
  • The manufacturer doesn’t ship this product to DC, NJ, VT, MA, and AK
  • The package may leak

This product won’t work in dry and hot weather. It is better to apply this weed killer when the temperature range outside is about 50-600F. The speed of action is only a few hours, sometimes 1-2 days.

The Buyer’s Guide

Pre-emergent or post-emergent?

Before applying any new product on your lawn to get rid of St. Augustine, make a plan. At first, you should choose between post-emergent and pre-emergent remedies:

  • Pre-emergent concoctions prevent weeds from growing;
  • Post-emergent remedies attack fully grown weeds;

Most users and tests of scientists prove that pre-emergent products are more effective for killing St. Augustine weeds. It is better to apply such remedies when the weather is dry and the daytime temperature is about 65-750F – February or March for the first time and September for the second time per year.

Read the label before buying or applying!

However, not all pre-emergent remedies are good for killing this particular weed type. Read the label directions and instructions – most products have the limits pointed out by manufacturers. Some products are good for broadleaf weeds only, the others work for creeping grass types.

Check the components

Most herbicides that contain 2,4-dichlorophenoxyacetic acid and Atrazine will destroy St. Augustine weed. Other components are not very effective.


What can you spray on St. Augustine to kill weeds?

There are a number of different weed killers that can be used on St. Augustine grass, but not all of them are created equal. You’ll want to select a product that is designed specifically for grass of this sort; using the incorrect sort of weed killer can harm or even destroy your lawn.

Some of the best weed killers for St. Augustine grass include products like Roundup For Lawns, Ortho Nutsedge Killer, and Scotts Turf Builder Weed & Feed. These products will kill most common weeds without harming your grass, and they’re easy to apply with a pump sprayer or hose-end applicator.

If you have stubborn weeds that just won’t die, you may need to resort to a stronger herbicide like Roundup QuickPRO. This product contains a higher concentration of glyphosate, so it’s more effective at killing tough weeds. However, if you don’t follow the instructions carefully, it can also harm your grass.

When should I apply weed and feed to St. Augustine?

To have the healthiest and best-looking lawn possible, you should apply weed and feed to your St. Augustine grass in early spring – before the weeds start to take over. You can also apply it in the late fall, after the last mowing of the season.

Weed and feed products typically contain a herbicide to kill existing weeds, and a fertilizer to nourish your grass. Be sure to read the label carefully before you buy, so you know what ingredients are in the product and how best to use it.

Will Roundup kill St. Augustine?

Roundup is a very effective weed killer and it will kill St. Augustine grass. However, you need to be careful when using it because it will also kill other plants that it comes in contact with. You should always read the label carefully and follow the directions exactly.

Roundup is a broad-spectrum herbicide that is used to kill weeds in gardens, lawns, and agricultural areas. Glyphosate is the main active component in dicamba, a non-selective herbicide. This means that it will kill most plants that it comes in contact with including St. Augustine grass.

You can use Roundup to spot treat weeds in your lawn without harming the surrounding grass. To do this, you need to buy a special Roundup applicator that has a small nozzle. This will allow you to apply the Roundup directly to the weed without harming the surrounding grass.

Video Tutorial: How to Remove Weeds from St. Augustine Grass

Final Thoughts

St. Augustine weed is not that hard to destroy. Use any of the above-mentioned remedies, according to the label direction. If you are not sure of the results, test a new herbicide on the small area free from good crops, flowers, vegetables, and fruits. The effect will become visible in a few days.